1. Technical Field
The present invention relates to a medium feeder which rotates to deliver a feed target medium while nipping the medium by a pair of discharge rollers, and a printer including this medium feeder.
2. Related Art
A tape printer (medium feeder) capable of rotating and delivering a printing tape while nipping the printing tape by a pair of discharge rollers (first roller and second roller) is known (see JP-A-2008-001065). This tape printer includes a pair of discharge rollers each of which has an outer circumferential surface made of conductive material and rotates to deliver a printing tape nipped between the pair of the discharge rollers, a pressing mechanism which relatively presses the pair of the discharge rollers in the direction of nipping the printing tape, and a continuity detecting unit connected with a pair of contacts contacting the conductive areas of the respective discharge rollers to detect continuity and discontinuity between the pair of the discharge rollers. The tape printer having this structure detects the presence of the printing tape passing between the pair of the discharge rollers, thereby determining arrival of the printing tape at the discharge rollers and discharge of the printing tape therefrom.
According to this type of medium feeder in the related art, however, the continuity detecting unit detects discontinuity based on adherence of foreign materials to the discharge rollers or insufficient contact between the discharge rollers even when the printing tape does not position between the discharge rollers. In this case, the presence or absence of the printing tape between the discharge rollers is difficult to be accurately determined.
In this type of medium feeder, it is conceivable that the second roller is configured to come close to and away from the first roller so as to securely position the feed target medium between the first roller and the second roller when a part of the feed target medium is located between the first and second rollers which nip the feed target medium and rotate to deliver the feed target medium so that the second roller is positioned away from the first roller when the feed target medium is set, and after the setting of the target medium, the second roller is moved close to the first roller to nip the target medium and rotate to deliver the target medium.
It is also conceivable to configure that the medium feeder includes: a first rotation body attached to a first roller shaft of the first roller; a second rotation body which engages with the first rotation body while overlapping therewith and disengages from the first rotation body in response to the presence of the feed target medium positioned between the first rotation body and the second rotation body; and a rotation body support member which supports the second rotation body in such a manner that the second rotation body can freely rotate around a second roller shaft of the second roller, and freely moves relative to the second roller between an advancing position where the second rotation body engages with the first rotation body and a retreating position where the second rotation body disengages from the first rotation body. In this case, the presence of the feed target medium between the first roller and the second roller can be detected based on the determination that the second rotation body has reached the retreating position, for example.
According to the structure, even if the second roller is moved to the separation position when a part of the set feed target medium positions between the first roller and the second roller which rotate to deliver the feed target medium while nipping the feed target medium therebetween, the space left between the first rotation body and the second rotation body is only a short clearance under the condition in which the second rotation body is located at the advancing position. In this case, the presence of the first rotation body and the second rotation body disturbs the setting of the feed target medium, and gives rise to the possibility that the feed target medium is set in a condition that the feed target medium does not enter the position between the first rotation body and the second rotation body.